Paper coating wax



:position polyethylene and a low molecular weight polyethylene as methyl ethyl ketone.

1 duce the oil content to-less 'than"0.5%

United States Patent PAPER COATING WAX Herman L. Thwaites, Clark, and Harold F. Hitchcox, Cranford, N. J., assignors to Standard Oil Development Company, a corporation of Delaware IM-Drawing. pplicatiolf April1 6, 1 952,

'SerialNo. 282,676 7 'Gla'ims. -(CL- 260- 285)" .This invention relates to a paper coating composition and relates more comprising a mixture containing a terminal hydroxyl :group'.

.Several typesof waxes may be derived from petroleum oils and in orderthatno confusion'willarisewith' respect .to the types of wax-employed in' this-invention, a"brief description -will'*begiven of the-method for preparing the wax used in the present invention.

The term paraffin 'wax is used to definethe hard,

xcrystallinewax commonly 'oltstained "from petroleum distillates derived from mineral'oils ofthemixed "base or parafiin base type. By the present "refining methods, "the :crude oil is subjected to "distillation whereby" it is separated into a series'of fractions, 'one of which is known as .parafi'in'distillatel The wax "is's'eparated from the asolvent as, 'for example, fPI'OPaIIE'OT arketone such "The wax obtained by either of these methods still contains from 10 to 50% oil and is generallyreferredwto as"slaek'-.wax. Thisrslack wax is subjected to a sweating operation to remove the oil. The resultingwaxusuallytcontains :3 1t'o .6% oil, but by proper sweating the oil may be as low as 1 to 3%. This wax known as crude scale waxis .again sweatedtoreand even-as low 215 0.05 This product is known as 'refined wax or paraflin wax-and-is graded according to tensile strength, melting point, oil content, hardness, etc.

It is known to add polyethylene to wax to prepare a suitable coating composition for paper and the like. The addition of polyethylene increases the blocking temperature of the wax, but does not affect the sealing strength to any great degree. On the other hand, the addition of low molecular weight droxyl group has less effect on the blocking temperature than regular polyethylene while the sealing strength is materially improved.

The polyethylene to be added in accordance with this invention should have a molecular weight of 4,000 to 25,000, preferably 12,000 to 13,000. The polyethylene having a terminal hydroxyl group should have a molecular weight of 500 to 10,000, preferably about 2,000. The polymers should be added in total amounts which ma range from 0.5 to 10.0%, preferably from 1.5 to 2.5%. The amount of each polymer may vary from 40 to 60% of the total.

The polyethylene having a terminal bond may be prepared in accordance with the disclosure in U. S. 2,504,400 issued April 18, 1950, to -M. Erchak, Jr. In general, the hydroxyl group is caused to enter the polymer chain by polyethylene having a terminal hyplaced in a clamp which .2. polymerizing ethylene under 425 to 475*atmospheresiat temperatures between 140 and 200: 0. in the' presence of=isopropanol :and hydrogen peroxide.

The following data illustrate -1the benefits do be tained iin accordance with this invention:

Example Wax blends =we1'e'p'rep'ared in 500 gram' quantities by first meltingparafiin waxhaving-za melting point of 132 and-then blending in the -.desired polymer while-.heating. Solutions were obtained in .15 to 201minut'es. attemperatures of .220-230'-F. The blends were' tthen 'sub- 'jected to seuffinggbloc'kingand sealing strength .tests.

1n the'scuff .test,--25 lbs. sulfite-bread wrap paper stock .to 1*4.lbs.- of waxper'rream and the paper allowed to conditionatleast24'hoursat- 713 F. at 50% relativelhumidity. i-Folcled-strips -1 in. x 4.5m. were then cut from the paper-and inserted in a Marathon Corporation scuff tester. One end of the paper strip was was fastened -.to a -sorew device to control its movement. The strip was then placed, while still clamped, between hard rubber pads covered with a clean abrasive tissue'paper. Thewhole assembly was loaded with .a 2kg. weight, andthe.stripwvaspulled between :the :tissues at a constant :rate. The scuff loss,'-reported .as-mg./1 0'0 sq. in., is calculated :from the :loss in-weight of the scutfed area.

The blocking test .is one of the conventional t-ype of blocking tests patternedafter the .Marathon Corporation .procedure. In this test the coated paper (same asthat usedin .thescuif test) was 'cutinto 1-.in..x 18 in. folded strips. These were placed between =unwaxed paper strips and the center portion was covered with a 1% :in. at '18 in. sponge .padand 3 linflx 1 .in. X6 in. steel weights. This assembly was placed in a constant temperature ovenat the estimatedblocking point. Additional-specimens were prepared in the .samemanner asiabove and placed in constant temperature ovens at a series of temperatures difrfering .by-a'bout '5 F. and bracketing the :estimated iblo'ck ing temperature. After .16 hours storage, the samples were removed and cooled under ,pressure. The test strips were then carefully-pulled apart =to.find 2- pairstested tat successive 5' temperatures, one showing "negligible'z-m'ar and the second showing considerableor completermar. The latter is taken as the blocking temperature.

The sealing strength was determined for papers waxed as in the above tests. In this case, 14 in. lengths are cut and folded with the test surfaces inwards. Fifteen 2 in. X 7 in. -folded strips were then cut for each wax sample and sealed on a 200 F. hot plate with a /2 in. diameter, 2% in. long steel roller weighing about gm. Ten of the sealed strips were immediately placed on a 73 F. metal plate to allow slow chilling of the seal. The other five strips were sealed and quickly plunged into water at 50 F. to quick-chill the seal. Each of the samples was then conditioned 16 to 20 hours at 73 F. and 50% relative humidity. A 1 in. X 4 in. strip was cut from the center of each. For the quick-pull, slow-chill test each of 5 strips was inserted in a Thwing Albert research tear tester and the sealing strength was read directly. The results for the 5 strips were averaged to obtained the final sealing strength value. For the slow pull method, 5 each of the quick and slow chilled samples were tested on a Socony-Vacuum type sealing tester in which a given load was placed on one end of the sealed strips and the unsealed flaps at the other end were pulled apart by strings hung over pulleys located about 6 in. apart but on the same horizontal plane. As the strings were pulled at a rate of 4 per minute, the specimen rose until it either and hydrogen peroxide.

The following data were obtained:

12,000-13000 mol. wt. polyethylene.

2.000 mol. wt. polyethylene having a terminal hydroxyl group.

The above data show that polyethylene raises the blocking point from 105 to 125 F., while polyethylene having a terminal hydroxyl group raises it only to 115-120 F. On the other hand, the sealing strength of the paper coated with the wax containing the polyethylene having a terminal hydroxyl group was materially better polyethylene. Despite the improved sealing strength of the Alcowax blend, the Alathon C blend would be more attractive commercially due to its higher blocking temperature. However, when these two materials are both blended into the wax not only are both the blocking temperature and the sealing strength increased as expectmore than would be be expected that the ed, but the increase in each is far calculated. For example, it would blend containing both Alathon C block at 120 F. unexpected improvement. Likewise, the sealing strength of the mixed blend would be expected to be 17 and 55 gms./in. by the quick and slow cooled method respectively. Actually it is the same as that obtained by the Alcowax alonenamely, 120 gms./in. this, the scuif resistance is not afiected adversely but actually improved slightly in some cases.

The nature of the present invention having been thus fully what cured by Letters Patent is:

1. A wax composition comprising parafiin wax containing from 0.5 to by weight of a mixture of polyethylene and 40 to 60% by weight based on total polymer of polyethylene having a terminal hydroxyl group, said hydroxylated polyethylene being produced by polymerizing ethylene under 425-475 atmospheres at temperatures between 140 and 200 C. in the presence of isopropanol and Alcowax would, Instead it blocks at 125 F.a most set forth and specific examples of the same given, is claimed as new and useful and desired to be se---' than that of the paper coated with the wax containing" In addition to 2. Composition according to claim 1 in which the polyethylene has a molecular weight of 4,00025,000 and the polyethylene having a terminal" hydroxyl group has a molecular weight of about 50010,000.

3. Composition according to claim 1 in which the polyethylene has a molecular weight of l2,00013,000 and the polyethylene having a terminal hydroxyl group has a molecular weight of about 2,000. 1

4. A wax composition comprising parafiin wax containing 1.5 to 2.5 by weight of a mixture of polyethylene and 40 to by weight based on total polymer of polyethylene having a terminal hydroxyl group, said hydroxylated polyethylene being produced by polymerizing ethylene under 425-475 atmospheres attemperatures between and 200 C. in the presence of isopropanol and hydrogen peroxide.

5. Composition according to claim 4 in which the polyethylene has a molecular weight of 4,00025,000 and the polyethylene having a terminal hydroxyl group has a molecular weight of about 500l0,000.

6. Composition according to claim 4 in which the polyethylene has a molecular weight of 12,000l3,000 and the polyethylene having a terminal hydroxyl group has a molecular weight of about 2,000.

7. Composition according to claim 6 in which the amount of the total polymers is about 2.5% by weight.

References Cited in the file of this patent.

UNITED STATES PATENTS Number Name Date 2,504,400 Erchack, Jr. Apr. 18, 1950 2,512,459 Hamilton June 20, 1950 2,551,087 Barnhart et al May 1, 1951 

1. A WAX COMPOSITION COMPRISING PARAFFIN WAX CONTAINING FROM 0.5 TO 10% BY WEIGHT OF A MIXTURE OF POLYETHYLENE AND 40 TO 60% BY WEIGHT BASED ON TOTAL POLYMER OF POLYETHYLENE HAVING A TERMINAL HYDROXYL GROUP, SAID HYDROXYLATED POLYETHYLENE BEING PRODUCED BY POLYMERIZING ETHYLENE UNDER 425-475 ATMOSPHERES AT TEMPERATURES BETWEEN 140* AND 200* C. IN THE PRESENCE OF ISOPROPANOL AND HYDROGEN PEROXIDE. 